Catalyst and method for hydrogenating carbonyl compounds

ABSTRACT

A process for the hydrogenation of an organic compound containing at least one carbonyl group comprises bringing the organic compound in the presence of hydrogen into contact with a shaped body which can be produced by a process in which
         (i) an oxidic material comprising copper oxide, zinc oxide and aluminum oxide is made available,   (ii) pulverulent metallic copper or pulverulent cement or a mixture thereof is added to the oxidic material, and   (iii) the mixture resulting from (ii) is shaped to form a shaped body.

This application is a 371 of PCT/EP00/08195, filed Aug. 22, 2000.

The present invention relates to a process for the hydrogenation oforganic compounds containing at least one carbonyl group using acatalyst in whose production copper powder or cement is added. Thepresent invention likewise relates to the catalyst itself and quitegenerally to the use of copper or cement powder in the production ofcatalysts having high selectivity combined with high stability.

The catalytic hydrogenation of carbonyl compounds such as carboxylicacids or carboxylic esters occupies an important position in theproduction lines of the basic chemicals industry.

In industrial processes, the catalytic hydrogenation of carbonylcompounds such as carboxylic esters is carried out virtually exclusivelyin fixed-bed reactors. Fixed-bed catalysts used are, apart fromcatalysts of the Raney type, especially support catalysts, for examplecopper, nickel or noble metal catalysts.

U.S. Pat. No. 3,923,694 describes, for example, a catalyst of the copperoxide/zinc oxide/aluminum oxide type. The disadvantage of this catalystis that it has insufficient mechanical stability during the reaction andtherefore disintegrates relatively quickly. This results in a drop inactivity and the building-up of a differential pressure over the reactordue to the disintegrating catalyst bodies. As a consequence, the planthas to be shut down prematurely.

DE 198 09 418.3 describes a process for the catalytic hydrogenation of acarbonyl compound in the presence of a catalyst comprising a support,which comprises predominantly titanium dioxide, and, as activecomponent, copper or a mixture of copper with at least one metalselected from the group consisting of zinc, aluminum, cerium, noblemetals and metals of transition group VIII, with the surface area ofcopper being not more than 10 m²/g. Preferred support materials aremixtures of titanium dioxide with aluminum oxide or zirconium oxide oraluminum oxide and zirconium oxide. In a preferred embodiment, thecatalyst material is shaped with addition of metallic copper powder.

DE-A 195 05 347 describes, quite generally, a process for producingcatalyst pellets having a high mechanical strength, with a metal powderor a powder of a metal alloy being added to the material to bepelletized. Aluminum powder or copper powder, inter alia, is added asmetal powder. However, in the case of a copper oxide/zinc oxide/aluminumoxide catalyst, the addition of aluminium powder gives a shaped bodywhich has poorer lateral compressive strength than a shaped bodyproduced without addition of aluminum powder, and, when used ascatalyst, the shaped body of the invention displayed a poorer conversionactivity than did catalysts produced without addition of aluminumpowder. The document likewise discloses a hydrogenation catalystcomprising NiO, ZrO₂, MoO₃ and CuO, in which Cu powder, inter alia, wasmixed during its production. However, this document gives no informationon the selectivity or the activity.

DD 256 515 describes a process for preparing alcohols from synthesis gasusing catalysts based on Cu/Al/Zn which are obtained by comilling andpelletization with metallic copper powder. The process described ismainly directed at the preparation of mixtures of C₁–C₅-alcohols, andthe process is carried out in a reactor whose upper third contains acatalyst having a relatively high proportion of copper powder and whoselower third contains a catalyst having a lower proportion of copperpowder.

It is an object of the present invention to overcome the disadvantagesof the prior art and to provide processes for the catalytichydrogenation of carbonyl compounds and to provide catalysts which haveboth a high mechanical stability and a high hydrogenation activity.

We have found that this object is achieved by mixing metallic copperpowder or cement powder or a mixture thereof into a dried oxidicmaterial made up of support material and active component and comprisingcopper oxide, zinc oxide and aluminum oxide and tableting the resultingmixture to give a shaped catalyst body which displays high activitiesand selectivities and has a high stability.

The present invention accordingly provides a process for thehydrogenation of an organic compound containing at least one carbonylgroup, which comprises bringing the organic compound in the presence ofhydrogen into contact with a shaped body which can be produced by aprocess in which

-   -   (i) an oxidic material comprising copper oxide, zinc oxide and        aluminum oxide is made available,    -   (ii) pulverulent metallic copper or pulverulent cement or a        mixture thereof is added to the oxidic material, and    -   (iii) the mixture resulting from (ii) is shaped to form a shaped        body.

In preferred embodiments, the shaped bodies of the present invention areused as uniform-composition catalysts, impregnated catalysts, coatedcatalysts and precipitated catalysts.

As support material in the catalyst of the present invention, preferenceis given to using a mixture of aluminum oxide, zinc oxide and possiblyzinc-aluminum spinel. There are no particular restrictions regarding thepreparation of the support material. In a preferred embodiment of theprocess of the present invention, an aqueous solution comprising zincnitrate and aluminum nitrate is reacted with sodium carbonate and theresulting suspension is filtered and dried, and particularly preferablyadditionally calcined in a further step.

In the catalysts used in the process of the present invention, theactive component copper and the active component zinc are applied to thesupport material used, without there being any restrictions in respectof the application method.

In particular, the following application methods are useful:

(A) Application of a copper salt solution and a zinc salt solution or asolution comprising copper and zinc salts to the prefabricated supportin one or more impregnation steps. Subsequent to the impregnation, thesupport is dried and, if appropriate, calcined.

A1) The impregnation can be carried out by the “incipient wetness”method in which the support is moistened with an amount of impregnationsolution corresponding to its water absorption capacity up tosaturation. However, impregnation can also be carried out with excesssolution.

A2) In the case of multistage impregnation methods, it is advantageousto carry out drying and, if appropriate, calcination between theindividual impregnation steps. The multistage impregnation isparticularly advantageous when the support is to be loaded with arelatively large amount of copper and/or a relatively large amount ofzinc.

A3) In the impregnation, the inorganic support material is preferablyused as a preshaped composition, for example as powder, spheres,extrudates or pellets. Particular preference is given to using it aspowder.

B) Precipitation of a copper salt solution and a zinc salt solution or asolution comprising copper and zinc salts onto the prefabricatedsupport. In a particularly preferred embodiment, this is present aspowder in an aqueous suspension.

B1) In one embodiment (I), a copper salt solution and a zinc saltsolution or a solution comprising copper and zinc salts is precipitated,preferably using sodium carbonate solution. An aqueous suspension of thesupport material is used as initial charge.

B2) In a further embodiment (II), the precipitated catalyst can beproduced in a multistage process. Here, in a first stage, a powder isprepared as described in A3) and dried. This powder is converted into anaqueous suspension and used as initial charge for a procedure equivalentto that described in embodiment (I).

Precipitates resulting from A) or B) are filtered and preferably washedfree of akali in a customary manner, as is described, for example, in DE198 09 418.3.

Both the end products from A) and those from B) are dried at from 50 to150° C., preferably at 120° C. and subsequently calcined if appropriate,preferably for 2 hours at generally from 200 to 600° C., in particularfrom 300 to 500° C.

As starting materials for A) and/or B), it is in principle known to useall Cu(I) and/or Cu(II) salts which are soluble in the solvents used forapplication to the support, for example nitrates, carbonates, acetates,oxalates or ammonium complexes and analogous zinc salts. For methods A)and B), particular preference is given to using copper nitrate.

In the process of the present invention, the above-described dried andpossibly calcined powder is preferably converted into pellets, rings,annular pellets, extrudates, honeycombs or similar shaped bodies. Allsuitable methods known from the prior art are conceivable for thispurpose.

The composition of the oxidic material is generally such that theproportion of copper oxide is in the range from 40 to 90% by weight, theproportion of zinc oxide is in the range from 10 to 50% by weight andthe proportion of aluminum oxide is up to 50% by weight, in each casebased on the total weight of the abovementioned oxidic constituents,with these three oxides together making up at least 80% by weight of theoxidic material after calcination and cement not being included as partof the oxidic material in the above sense.

In a preferred embodiment, the present invention accordingly provides aprocess as described in which the oxidic material comprises

-   -   (a) copper oxide in a proportion in the range 60≦x≦80% by        weight, preferably 65≦x≦75% by weight,    -   (b) zinc oxide in a proportion in the range 15≦y≦35% by weight,        preferably 20≦y≦30% by weight, and    -   (c) aluminum oxide in a proportion in the range 2≦z≦20% by        weight, preferably 3≦z≦7% by weight,    -   in each case based on the total weight of the oxidic material        after calcination, where 80≦x+y+z≦100, in particular        95≦x+y+z≦100, and cement is not included as part of the oxidic        material in the above sense.

The process of the present invention and the catalysts of the presentinvention are distinguished by the addition of pulverulent copper orpulverulent cement or a mixture thereof as additive to the oxidicmaterial prior to shaping.

In general, the amount of pulverulent copper or pulverulent cement or amixture thereof added to the oxidic material is in the range from 1 to40% by weight, preferably in the range from 2 to 20% by weight andparticularly preferably in the range from 5 to 10% by weight, in eachcase based on the total weight of the oxidic material.

The present invention therefore also provides a process as describedabove in which the pulverulent metallic copper or the pulverulent cementor the mixture thereof is added in an amount in the range from 1 to 40%by weight, based on the total weight of the oxidic material.

The particle size of the copper powder or the cement powder is generallyin the range from 0.1 to 1000 μm, preferably in the range from 0.5 to500 μm and particularly preferably in the range from 1 to 300 μm.

In a preferred embodiment, use is made of copper powder and cementpowder having a particle size distribution in which at least 45%,preferably at least 70%, particularly preferably at least 90%, of thecopper or cement particles have particle sizes in the range from 10 to100 μm.

The particle sizes are measured using a particle size measurementinstrument model “HELOS 12KA/LA” from SYMPATEC. The SYMPATEC HELOSsystem employs the optical principle of laser light scattering for therapid analysis of particle size distributions in suspensions, emulsions,aerosols and sprays. The HELOS measurement system comprises an opticalarrangement in which laser, beam expander, measuring station, focussinglens and multielement photodetector are arranged in succession along theoptical axis. The focussing lens positioned subsequently in the beampath positioned in the beam path collects the Fraunhofer scatteringspectra produced by the particles and focusses them on the centrallyarranged multielement photodetector. Depending on the particle sizedistribution, a radially symmetric intensity distribution whose energydensity decreases with distance from the center and whose distributionis determined by the number and size of the particles in the measurementvolume is formed. The intensity distribution is recorded by means of themultielement detector comprising 31 semicircular rings, converted intovoltage-proportional values, stored in a subsequent data processor andtaken over for further evaluation. From the measured intensities, theassociated particle size distribution can be calculated by solution of asystem of simultaneous linear equations.

The surface area of the copper powder or cement powder, determined bythe BET method, is generally in the range from 0.01 to 20 m²/g,preferably in the range from 0.05 to 10 m²/g, particularly preferably inthe range from 0.1 to 0.5 m²/g.

The present invention therefore also provides a process as describedabove in which the particle size of the pulverulent copper and thepulverulent cement is in the range from 0.1 to 1000 μm and the BETsurface area is in the range from 0.01 to 2 m²/g.

As cement, preference is given to using an alumina cement. The aluminacement particularly preferably consists essentially of aluminum oxideand calcium oxide, in particular it comprises from about 75 to 85% byweight of aluminum oxide and from about 15 to 25% by weight of calciumoxide. It is also possible to use a cement based on magnesiumoxide/aluminum oxide, calcium oxide/silicon oxide and calciumoxide/aluminum oxide/iron oxide.

In particular, the oxidic material may further comprise a proportion ofnot more than 10% by weight, preferably not more than 5% by weight,based on the total weight of the oxidic material, of at least oneadditional component selected from the group consisting of the elementsRe, Fe, Ru, Co, Rh, Ir, Ni, Pd and Pt.

In a further preferred embodiment of the process of the invention,graphite is added in addition to the copper powder or the cement powderor the mixture thereof to the oxidic material prior to shaping to formthe shaped body. Preference is given to adding such an amount ofgraphite that shaping to form a shaped body can be carried out morereadily. In a preferred embodiment, from 0.5 to 5% by weight ofgraphite, based on the total weight of the oxidic material, is added.Here, it is immaterial whether the graphite is added to the oxidicmaterial before or after or simultaneously with the copper powder or thecement powder or the mixture thereof.

The present invention accordingly also provides a process as describedabove in which graphite in an amount of from 0.5 to 5% by weight, basedon the total weight of the oxidic material, is added to the oxidicmaterial or the mixture resulting from (ii).

In a preferred embodiment, the present invention therefore also providesa shaped body comprising

-   -   an oxidic material comprising    -   (a) copper oxide in a proportion in the range 60≦x≦80% by        weight, preferably 65≦x≦75% by weight,    -   (b) zinc oxide in a proportion in the range 15≦y≦35% by weight,        preferably 20≦y≦30% by weight, and    -   (c) aluminum oxide in a proportion in the range 2≦z≦20% by        weight, preferably 3≦z≦7% by weight,    -   in each case based on the total weight of the oxidic material        after calcination, where 80≦x+y+z≦100, in particular        95≦x+y+z≦100,    -   metallic copper powder or cement powder or a mixture thereof in        a proportion in the range from 1 to 40% by weight, based on the        total weight of the oxidic material, and    -   graphite in a proportion of from 0.5 to 5% by weight, based on        the total weight of the oxidic material,    -   where the sum of the proportions of oxidic material, metallic        copper powder or cement powder or a mixture thereof and graphite        makes up at least 95% by weight of the shaped body.

After addition of the copper powder or the cement powder or the mixturethereof and, if desired, graphite to the oxidic material, the shapedbody obtained after shaping is, if desired, calcined at least once for aperiod of generally from 0.5 to 10 hours, preferably from 0.5 to 2hours. The temperature in this calcination step or steps is generally inthe range from 200 to 600° C., preferably in the range from 250 to 500°C. and particularly preferably in the range from 300 to 400° C.

In the case of shaping using cement powder, it may be advantageous tomoisten the shaped body obtained before calcination with water andsubsequently to dry it.

When the shaped body is used as catalyst in the oxidic form, it isprereduced by means of reducing gases, for example hydrogen, preferablyhydrogen/inert gas mixtures, in particular hydrogen/nitrogen mixtures,at from 100 to 500° C., preferably from 150 to 350° C. and in particularfrom 180 to 200° C., prior to being brought into contact with thehydrogenation solution. This is preferably carried out using a mixturehaving a hydrogen content in the range from 1 to 100% by volume,particularly preferably in the range from 1 to 50% by volume.

In a preferred embodiment, the shaped body of the invention is activatedin a manner known per se by treatment with reducing media prior to useas catalyst. The activation is carried out either beforehand in areduction oven or after installation in the reactor. If the catalyst hasbeen activated beforehand in the reduction oven, it is installed in thereactor and supplied directly with the hydrogenation solution underhydrogen pressure.

A preferred area of application of the shaped bodies produced by theprocess of the present invention is the hydrogenation of organiccompounds containing carbonyl groups in a fixed bed. However, otherembodiments such as a fluidized-bed reaction using catalyst material inupward and downward swirling motion are likewise possible. Thehydrogenation can be carried out in the gas phase or in the liquidphase. The hydrogenation is preferably carried out in the liquid phase,for example in the downflow mode or upflow mode.

When the hydrogenation is carried out in the downflow mode, the liquidstarting material comprising the carbonyl compound to be hydrogenated isallowed to trickle over the catalyst bed in the reactor which is underhydrogen pressure, forming a thin liquid film on the catalyst. On theother hand, when the hydrogenation is carried out in upflow mode,hydrogen is introduced into the reactor flooded with the liquid reactionmixture and the hydrogen passes through the catalyst as rising gasbubbles.

In one embodiment, the solution to be hydrogenated is pumped over thecatalyst bed in a single pass. In another embodiment of the process ofthe present invention, part of the product is continuously taken off asproduct stream after passing through the reactor and, if desired, ispassed through a second reactor as defined above. The other part of theproduct is combined with fresh starting material comprising the carbonylcompound and fed back into the reactor. This mode of operation willhereinafter be referred to as the circulation mode.

If the downflow mode is chosen as embodiment of the present invention,the circulation mode is preferred. Further preference is given tocarrying out the hydrogenation in the circulation mode using a mainreactor and an after-reactor.

The process of the present invention is suitable for the hydrogenationof carbonyl compounds such as aldehydes and ketones, carboxylic acids,carboxylic esters or carboxylic anhydrides to give the correspondingalcohols, with preference being given to aliphatic and cycloaliphatic,saturated and unsaturated carbonyl compounds. In the case of aromaticcarbonyl compounds, formation of undesirable by-products byhydrogenation of the aromatic ring may occur. The carbonyl compounds maybear further functional groups such as hydroxyl or amino groups.Unsaturated carbonyl compounds are generally hydrogenated to thecorresponding saturated alcohols. The term “carbonyl compounds” used inthe context of the invention encompasses all compounds containing a C═Ogroup, including carboxylic acids and their derivatives. Of course, itis also possible to hydrogenate mixtures of two or more carbonylcompounds. Furthermore, each individual carbonyl compound to behydrogenated can also contain more than one carbonyl group.

The process of the present invention is preferably used for thehydrogenation of aliphatic aldehydes, hydroxyaldehydes, ketones, acids,esters, anhydrides, lactones and sugars.

Preferred aliphatic aldehydes are branched and unbranched, saturatedand/or unsaturated aliphatic C₂–C₃₀-aldehydes, which are obtainable, forexample, by means of the oxo process from linear or branched olefinshaving internal or terminal double bonds. It is also possible tohydrogenate oligomeric compounds containing more than 30 carbonylgroups.

Examples of aliphatic aldehydes are:

Formaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde,valeraldehyde, 2-methylbutyraldehyde, 3-methylbutyraldehyde(isovaleraldehyde), 2,2-dimethylpropionaldehyde (pivalaldehyde),caproaldehyde, 2-methylvaleraldehyde, 3-methylvaleraldehyde,4-methylvaleraldehyde, 2-ethylbutyraldehyde, 2,2-dimethylbutyraldehyde,3,3-dimethylbutyraldehyde, caprylic aldehyde, capric aldehyde,glutaraldehyde.

Apart from the short-chain aldehydes mentioned, long-chain aliphticaldehydes as can be obtained, for example, by means of the oxo processfrom linear α-olefins, are also particularly suitable.

Particular preference is given to enalization products such as2-ethylhexenal, 2-methylpentenal, 2,4-diethyloctenal or2,4-dimethylheptenal.

Preferred hydroxyaldehydes are C₃–C₁₂-hydroxyaldehydes as areobtainable, for example, from aliphatic and cycloaliphatic aldehydes andketones by aldol reaction with themselves or formaldehyde. Examples are3-hydroxypropanal, dimethylolethanal, trimethylol-ethanal(pentaerythrital), 3-hydroxybutanal (acetaldol),3-hydroxy-2-ethylhexanal (butyl aldol), 3-hydroxy-2-methylpentanal(propene aldol), 2-methylolpropanal, 2,2-dimethylolpropanal,3-hydroxy-2-methylbutanal, 3-hydroxypentanal, 2-methylolbutanal,2,2-dimethylolbutanal, hydroxypivalaldehyde. Particular preference isgiven to hydroxypivalaldehyde (HPA) and dimethylolbutanal (DMB).

Preferred ketones are acetone, butanone, 2-pentanone, 3-pentanone,2-hexanone, 3-hexanone, cyclohexanone, isophorone, methyl isobutylketone, mesityl oxide, acetophenone, propiophenone, benzophenone,benzal-acetone, dibenzalacetone, benzalacetophenone, 2,3-butanedione,2,4-pentanedione, 2,5-hexanedione and methyl vinyl ketone.

Furthermore, carboxylic acids and derivatives thereof, preferably thosehaving 1–20 carbon atoms, can be reacted. In particular, the followingmay be mentioned:

-   -   carboxylic acids such as formic acid, acetic acid, propionic        acid, butyric acid, isobutyric acid, n-valeric acid,        trimethylacetic acid (“pivalic acid”), caproic acid, enanthic        acid, caprylic acid, capric acid, lauric acid, myristic acid,        palmitic acid, stearic acid, acrylic acid, methacrylic acid,        oleic acid, elaidic acid, linoleic acid, linolenic acid,        cyclohexanecarboxylic acid, benzoic acid, phenylacetic acid,        o-toluic acid, m-toluic acid, p-toluic acid, o-chlorobenzoic        acid, p-chlorobenzoic acid, o-nitrobenzoic acid, p-nitrobenzoic        acid, salicylic acid, p-hydroxybenzoic acid, anthranilic acid,        p-aminobenzoic acid, oxalic acid, malonic acid, succinic acid,        glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic        acid, sebacic acid, maleic acid, fumaric acid, phthalic acid,        isophthalic acid, terephthalic acid;    -   carboxylic esters such as the C₁–C₁₀-alkyl esters of the        abovementioned carboxylic acids, in particular methyl formate,        ethyl acetate, butyl butyrate, dialkyl esters of phthalic acid,        isophthalic acid, terephthalic acid, adipic acid and maleic        acid, e.g. the dimethyl esters of these acids, methyl        (meth)acrylate, butyrolactone, caprolactone and polycarboxylic        esters, e.g. polyacrylic and polymethacrylic esters and their        copolymers, and polyesters, e.g. polymethyl methacrylate or        terephthalic esters, and other industrial plastics; in these        cases, the reactions carried out are, in particular,        hydrogenolyses, i.e. the reaction of esters to form the        corresponding acids and alcohols;    -   fats;    -   carboxylic anhydrides such as the anhydrides of the        abovementioned carboxylic acids, in particular acetic anhydride,        propionic anhydride, benzoic anhydride and maleic anhydride;    -   carboxamides such as formamide, acetamide, propionamide,        stearamide, terephthalamide.

It is also possible for hydroxycarboxylic acids, e.g. lactic, malic,tartaric or citric acid, or amino acids, e.g. glycine, alanine, prolineand arginine, and peptides to be reacted.

As particularly preferred organic compounds, saturated or unsaturatedcarboxylic acids, carboxylic esters, carboxylic anhydrides or lactonesor mixtures of two or more thereof are hydrogenated.

The present invention therefore also provides a process as describedabove in which the organic compound is a carboxylic acid, a carboxylicester, a carboxylic anhydride or a lactone.

Examples of these compounds are, inter alia, maleic acid, maleicanhydride, succinic acid, succinic anhydride, adipic acid,6-hydroxycaproic acid, 2-cyclododecylpropionic acid, the esters of theabovementioned acids, for example the methyl, ethyl, propyl or butylester. Further examples are γ-butyrolactone and caprolactone.

In a very particularly preferred embodiment, the present inventionprovides a process as described above in which the organic compound isadipic acid or an ester of adipic acid.

The carbonyl compound to be hydrogenated can be fed to the hydrogenationreactor either alone or as a mixture with the product of thehydrogenation reaction, and can be fed in in undiluted form or using anadditional solvent. Suitable additional solvents are, in particular,water and alcohols such as methanol, ethanol and the alcohol formedunder the reaction conditions. Preferred solvents are water, THF andNMP; particular preference is given to water.

The hydrogenation both in the upflow mode and in the downflow mode, ineach case preferably in the circulation mode, is generally carried outat from 50 to 350° C., preferably from 70 to 300° C., particularlypreferably from 100 to 270° C., and a pressure in the range from 3 to350 bar, preferably in the range from 5 to 330 bar, particularlypreferably in the range from 10 to 300 bar.

In a very particularly preferred embodiment, the catalysts of thepresent invention are used in processes for preparing hexanediol and/orcaprolactone, as are described in DE 196 07 954, DE 196 07 955, DE 19647 348 and DE 196 47 349.

High conversions and selectivities are achieved in the process of thepresent invention using the catalysts of the present invention. At thesame time, the catalysts of the present invention have a high chemicaland mechanical stability. The advantageous abrasion behavior, which isreflected in low abrasion values, is of particular importance here.

The present invention therefore provides quite generally for the use ofpulverulent metallic copper or pulverulent cement or a mixture thereofas additive in the production of a catalyst for increasing both themechanical stability and the activity and selectivity of the catalyst.

In a preferred embodiment, the present invention provides for the use asdescribed above of such a catalyst comprising copper as activecomponent.

The mechanical stability of solid-state catalysts and specifically thecatalysts of the present invention is described by the parametersabrasion and lateral compressive strength.

The lateral compressive strength was determined for the purposes of thepresent patent application by means of a “Z 2.5/T 919” instrument ofZwick (Ulm), and the abrasion was determined in accordance with ASTMDesignation D 4058-81. In the case of both the reduced catalysts and theused catalysts, the measurement were carried out under a nitrogenatmosphere so as to avoid reoxidation of the catalysts.

The following examples illustrate the invention.

EXAMPLES Example 1 Production of Catalyst 1

Production of the Support

450 g of Al(NO₃)₃*9H₂O were added to 649 g of a well-stirred aqueoussolution of zinc nitrate having a zinc content of 14.5% by weight andthe mixture was made up to a volume of 1.25 l with water in order todissolve the aluminum salt (solution A). In a separate vessel, 474 g ofanhydrous sodium carbonate were dissolved in water and the solution wasmade up to 2 l with water (solution B).

Solution A and solution B were heated to 50° C. and fed via separatelines into a precipitation vessel containing a well-stirred solution of20 g of NaHCO₃ in 350 ml of water which had been heated to 50° C. The pHwas brought to 6.8 over a period of about 3 minutes by appropriateadjustment of the feed rates of the solutions A and B. While keeping thepH constant at 6.8 and maintaining the temperature at 50° C., all ofsolution A was reacted with sodium carbonate. The suspension formed inthis way was subsequently stirred for 3 hours, with the pH beingmaintained at 6.8 by occasional addition of dilute nitric acid. Thesuspension was filtered and washed with distilled water until thenitrate content of the washings was <10 ppm. The filter cake was driedat 120° C. for 16 hours and subsequently calcined at 425° C. for 1 hour.

Production of the Catalyst

A mixture of 432 g of a nitric acid solution of copper nitrate having acopper content of 15.5% by weight and 95 g of a nitric acid solution ofzinc nitrate having a zinc content of 14.5% by weight was diluted withwater to a volume of 500 ml and heated to 70° C. While stirring, 25.1 gof the above-described pulverulent calcined support was slowly addedover a period of about 5 minutes and the resulting milky suspension wasstirred for 15 minutes (suspension C).

In a separate vessel, 474 g of anhydrous sodium carbonate were dissolvedin water and the solution was made up to 2 l with water and heated to70° C. (solution D). Suspension C and solution D were fed via separatelines into a precipitation vessel which was provided with a stirrer andcontained 350 ml of water heated to 70° C. The pH was brought to 7.4 byappropriate adjustment of the feed rates of the suspension C andsolution D.

While keeping the pH constant at 7.4 and maintaining a temperature of70° C., all of suspension C was reacted with sodium carbonate. Thesuspension formed in this way was subsequently stirred for another 2hours, with the pH being maintained at 7.4 by occasional addition ofdilute nitric acid or sodium carbonate solution D. The suspension wasfiltered and washed with distilled water until the nitrate content ofthe washings was <10 ppm.

The filter cake was dried at 120° C. for 16 hours and subsequentlycalcined at 430° C. for 1 hour. The brownish black catalyst powderobtained in this way was mixed with 1.5% by weight of graphite and 5% byweight of copper powder (grade FFL No. 10914 from NorddeutscheAffinerie, having a BET surface area of 0.23 m²/g and a particle sizedistribution in which 92% of the particles lie in a size range from 10to 100 μm) and pressed to form pellets having a diameter of 3 mm and aheight of 3 mm. The pellets were finally calcined at 330° C. for 1 hour.

The catalyst produced in this way has the chemical composition 66%CuO/24% ZnO/5% Al₂O₃/5% Cu. The lateral compressive strength and theabrasion in the oxidic and reduced states are shown in Table 1.

Example 2 Hydrogenation of Dimethyl Adipate Over Catalyst 1

Dimethyl adipate was hydrogenated continuously in the downflow mode withrecirculation (feed/recycle ratio=10/1) at a WHSV of 0.5 kg/(1*h), apressure of 240 bar and reaction temperatures of 200° C. and 220° C. ina vertical tube reactor charged with 200 ml of catalyst 1. Theexperiment was carried out for a total time of 14 days. GC analysisfound ester conversions of 99% and 100%, hexanediol contents of 57% and62% and methanol contents of 30% and 31% in the reaction product at 200°C. and 220° C., respectively. After removal from the reactor, thecatalyst was found to be still completely intact and had a highmechanical stability. Lateral compressive strength and abrasion areshown in Table 1. The experimental results are summarized once more inTable 2.

Example 3 Production of Catalyst 2

Catalyst 2 was produced using a method analogous to that for catalyst 1in Example 1, but 10% of copper powder of the grade Unicoat 2845 fromSchlenck having a BET surface area of 2.34 m²/g and a particle sizedistribution in which 77% of the particles lie in the size range from 10to 100 μm was added and the pellets were calcined at 400° C.

The catalyst produced in this way has the chemical composition 63%CuO/22% ZnO/5% Al₂O₃/10% Cu. The lateral compressive strength and theabrasion in the oxidic and reduced states are shown in Table 1.

Example 4 Hydrogenation of Dimethyl Adipate Over Catalyst 2

Dimethyl adipate was hydrogenated continuously in the downflow mode withrecirculation (feed/recycle ratio=10/1) at a WHSV of 0.5 kg/(1*h), apressure of 240 bar and reaction temperatures of 200° C. and 220° C. ina vertical tube reactor charged with 200 ml of catalyst 2. Theexperiment was carried out for a total time of 14 days. GC analysisfound ester conversions of 98% in each case, hexanediol contents of 55%and 59% and methanol contents of 26% and 28% in the reaction product at200° C. and 220° C., respectively. After removal from the reactor, thecatalyst was found to be still completely intact and had a highmechanical stability. Lateral compressive strength and abrasion areshown in Table 1. The experimental results are summarized once more inTable 2.

Example 5

Catalyst 3 was produced using a method analogous to that for catalyst 2in Example 3, but 5% of Secar cement grade 80 from Lafarge having a BETsurface area of 7.5 m²/g and a particle size distribution in which 49%of the particles lie in the size range from 10 to 100 μm was added. Thepellets were moistened for 6 hours, dried in air and subsequentlycalcined at 400° C. for 2 hours.

The catalyst produced in this way has the chemical composition 66%CuO/24% ZnO/5% Al₂O₃/5% cement. The lateral compressive strength and theabrasion in the oxidic and reduced states are shown in Table 1.

Example 6 Hydrogenation of Dimethyl Adipate Over Catalyst 3

Dimethyl adipate was hydrogenated continuously in the downflow mode withrecirculation (feed/recycle ratio=10/1) at a WHSV of 0.5 kg/(1*h), apressure of 240 bar and reaction temperatures of 200° C. and 220° C. ina vertical tube reactor charged with 200 ml of catalyst 3. Theexperiment was carried out for a total time of 14 days. GC analysisfound ester conversions of 94% and 97%, hexanediol contents of 50% and57% and methanol contents of 26% and 28% in the reaction product at 200°C. and 220° C., respectively. After removal from the reactor, thecatalyst was found to be still completely intact and had a highmechanical stability. Lateral compressive strength and abrasion areshown in Table 1. The experimental results are summarized once more inTable 2.

Example 7 Production of a Comparative Catalyst

The catalyst was produced exactly as described in Example 1 of U.S. Pat.No. 3,923,694. The catalyst produced in this way had the chemicalcomposition 70% CuO/25% ZnO/5% Al₂O₃. The lateral compressive strengthand the abrasion in the oxidic and reduced states are shown in Table 1.

Example 8 Hydrogenation of Dimethyl Adipate Over the ComparativeCatalyst

Dimethyl adipate was hydrogenated continuously in the downflow mode withrecirculation (feed/recycle ratio=10/1) at a WHSV of 0.5 kg/(1*h), apressure of 240 bar and reaction temperatures of 200° C. and 220° C. ina vertical tube reactor charged with 200 ml of the comparative catalyst.The experiment was carried out for a total time of 14 days. GC analysisfound ester conversions of 92% and 96%, hexanediol contents of 48% and58% and methanol contents of 25% and 28% in the reaction product at 200°C. and 220° C., respectively. After removal from the reactor, thecatalyst was still completely intact but the mechanical stability hadbeen reduced considerably. Lateral compressive strength and abrasion areshown in Table 1. The experimental results are summarized in Table 2.

TABLE 1 Lateral Abrasion Lateral Lateral compressive (after removal com-Abrasion comp- Abrasion strength from the pressive (oxidic)/ ressivereduced)/ (after removal reactor)/ strength % by strength % by from the% by Catalyst (oxidic)/kg weight (reduced)/kg weight reactor)/kg weightCatalyst 5.5 3.2 3.9 1.2 4.3 1.8 1 Catalyst 18.2 1.5 6.7 2.0 2.0 3.9 2Catalyst 6.3 2.3 3.9 3.5 4.0 1.2 3 Compar- 12.1 0.4 4.8 12.3 3.8 94.5ative catalyst

The data in Table 1 show that the novel catalysts 1 to 3 display asignificantly higher mechanical stability, in particular significantlylower abrasion values, than the comparative catalyst both in the reducedstate and after removal from the reactor.

The data in Table 2 below show that the catalysts of the presentinvention have considerably higher hydrogenation activities, i.e. higherconversions of dimethyl adipate, at 200° C. and 220° C. than thecomparative catalyst, and also tend to give higher selectivities to thedesired product, i.e. higher contents of the target products hexanedioland methanol in the output from the reactor.

TABLE 2 Hexanediol Methanol Reaction Conversion content in the contentin the tempera- of dimethyl reaction reaction Catalyst ture/° C.adipate/% product/% product/% Catalyst 1 200 99 57 30 220 100 62 31Catalyst 2 200 98 55 26 220 98 59 28 Catalyst 3 200 94 50 26 220 97 5728 Compara- 200 92 48 25 tive 220 96 58 28 catalyst

1. A process for the hydrogenation of an organic compound containing atleast one carbonyl group, which comprises bringing the organic compoundin the presence of hydrogen into contact with a shaped body which isproduced by a process in which (i) an oxidic material comprising copperoxide, zinc oxide and aluminum oxide is made available, (ii) pulverulentmetallic copper or pulverulent cement or a mixture thereof is added tothe oxidic material, and (iii) the mixture resulting from (ii) is shapedto form a shaped body.
 2. A process as claimed in claim 1, wherein theoxidic material comprises (a) copper oxide in a proportion x in therange from 60 to 80% by weight, (b) zinc oxide in a proportion y in therange from 15 to 35% by weight, and (c) aluminum oxide in a proportion zin the range from 2 to 20% by weight, in each case based on the totalweight of the oxidic material after calcination, where x+y+z is in therange from 80 to 100% by weight, and cement is not included as part ofthe oxidic material in the above sense.
 3. A process as claimed in claim1, wherein the pulverulent metallic copper or the pulverulent cement orthe mixture thereof is added in an amount in the range from 1 to 40% byweight, based on the total weight of the oxidic material.
 4. A processas claimed in claim 1 wherein the particle size of the pulverulentcopper and of the pulverulent cement is in the range from 0.1 to 100 μm.5. A process as claimed in claim 1, wherein graphite is added in anamount in the range from 0.5 to 5% by weight, based on the total weightof oxidic material, to the oxidic material or the mixture resulting from(II).
 6. A process as claimed in claim 1, wherein the organic compoundis a carboxylic acid, a carboxylic ester, a carboxylic anhydride or alactone.
 7. A process as claimed in claim 6, wherein the organiccompound is adipic acid or an ester of adipic acid.